Matthew Barnbrook

1 INTRODUCTION Parallel evolution has provided important insights into the mechanisms of adaptation (Arendt & Reznick, 2008; Blount et al., 2018; James et al., 2023; Stern & Orgogozo, 2009) and has helped to identify adaptive characters and the underlying mutations and selective agents (e.g. Konečná et al., 2021; Rennison et al., 2019).

Highlights • Hairy encodes a trichome-repressing glutaredoxin • Phased Hairy expression determines which tissues are bald • Hairy alpine Antirrhinum species lack Hairy function • Old hairy mutations were used in evolution of new alpine species Summary Most angiosperms produce trichomes—epidermal hairs that have protective or more specialized roles. Trichomes are multicellular in almost all species and, in the majority, secretory.